1. Field of the Invention
The present invention relates to a nozzle plate, a method of manufacturing a nozzle plate, and an image forming apparatus, and more particularly, to a nozzle plate and a method of manufacturing a nozzle plate used for the ejection surface of a print head of an inkjet type of image forming apparatus, or the like.
2. Description of the Related Art
An image forming apparatus of an inkjet type has been commonly known which includes a print head provided with a nozzle plate in which a plurality of nozzles are formed. The nozzle plate has an ejection surface that opposes the recording medium. The nozzle plate is typically provided with a liquid-phobic film on the ejection surface opposing the recording medium, in order to stabilize the ejection direction and improve the ejection performance of the ink droplets.
Here, if a liquid-phobic film is formed only on the ejection surface which opposes the recording medium, then the meniscus of the ink inside the nozzles is positioned in the vicinity of the ejection surface or at an indeterminate position inside the nozzle. Therefore, if the meniscus of the ink inside the nozzle is positioned in the vicinity of the ejection surface, then fine dust present outside the nozzle hole, and paper fibers generated from the recording medium, and the like, are liable to adhere to the ink inside the nozzle. Furthermore, if the meniscus of the ink inside the nozzle is situated at an indeterminate position inside the nozzle, then it becomes difficult to control the position of the meniscus and it is difficult to achieve a uniform meniscus position in all of the nozzles. Consequently, the ejection state of the ink droplets varies for each nozzle, and there is a possibility that this will lead to decline in the ejection performance of the ink droplets.
Japanese Patent Application Publication No. 7-125220 discloses a nozzle plate and a method of manufacturing a nozzle plate. FIG. 13 is an enlarged view of the vicinity of a nozzle 224 in the nozzle plate disclosed in Japanese Patent Application Publication No. 7-125220. As shown in FIG. 13, the nozzle plate described in Japanese Patent Application Publication No. 7-125220 is constituted of a nozzle plate substrate 230 having an ejection surface 230A that is covered with a liquid-phobic film 227 and opposes the recording medium. Moreover, a portion of the inner surface of the nozzle 224 is also covered with the liquid-phobic film 227.
FIGS. 14A to 14D are diagrams showing a method of manufacturing the nozzle plate described in Japanese Patent Application Publication No. 7-125220. As shown in FIG. 14A, firstly, a photosensitive resin film 228 is pressure bonded to the rear surface 230B of a nozzle plate substrate 230 (the ink droplet ejection surface being taken as a front surface 230A).
Next, as shown in FIG. 14B, the photosensitive resin film 228 is cured by radiating ultraviolet light on both the front surface 230A and the rear surface 230B of the nozzle plate substrate 230, whereupon a eutectic plated layer 225 is formed on the front surface 230A of the nozzle plate substrate 230. In so doing, as shown in FIG. 14C, a portion of the eutectic plating 225 enters inside the nozzle 224, but the amount of plating entering in this fashion is restricted by the photosensitive resin film 228 having been cured in the step shown in FIG. 14B. Thereupon, as shown in FIG. 14D, the photosensitive resin film 228 which is present on the rear surface 230B of the nozzle plate substrate 230 and has entered inside the nozzle 224 is dissolved and removed with a solvent, whereupon the nozzle plate is heated. Consequently, the ink-repelling plated layer is obtained on the front surface 230A of the nozzle plate substrate 230 and inside the nozzle 224.
However, the invention described in Japanese Patent Application Publication No. 7-125220 involves the following problems.
In the invention in Japanese Patent Application Publication No. 7-125220, the liquid-phobic film 227 is formed on the front surface of the nozzle plate substrate 230 and the inner surface of the nozzles 224. Therefore, if excessive pressure is applied to the ink inside the nozzle 224 to perform refilling of the ink into the print head (not illustrated), or the like, and the meniscus consequently breaks down, then there is a possibility that ink may flow out from the position of the boundary of the liquid-phobic film 227 inside the nozzle 224, onto the front surface 227A of the nozzle plate, thus leading to deterioration in the ink droplet ejection characteristics.
Moreover, in cases where a minute vibration is applied to the meniscus in order to prevent problems such as blockages caused by increased viscosity of the ink in the vicinity of the nozzle 224 due to a prolonged period without ejection of ink droplets, then it is difficult to maintain the meniscus position in a stable state, and there is a possibility that this will lead to deterioration in the ink droplet ejection characteristics.
Furthermore, the amount of liquid-phobic film 227 which enters into the nozzle 224 is controlled by adjusting the amount of the photosensitive resin film 228 to enter inside the nozzle 224 and become cured. However, due to the effects of the error in the accuracy of the opening section of the nozzle 224, and the effects of the wetting properties of the interior of the nozzle 224, the amount by which the photosensitive resin film 228 enters into the nozzle 224 varies, and the amount by which the liquid-phobic film 227 enters into the nozzle 224 also varies accordingly. Consequently, it is difficult to accurately control the position at which the meniscus is held inside the nozzle 224, and there is a possibility that this will lead to deterioration of the ink droplet ejection characteristics.